Thread TypesCommonly used threads having the triangular cross sections for fastening are the metric screw threads and the Unified screw threads. Based on the pitch of the thread, there are coarse threads and fine threads while the pitches of fine threads are shorter than the pitches of coarse threads.

Pipe threads are mainly used for the mechanical linkage to connect pipe parts and fluidic devices. There are two types of pipe threads, parallel threads and taper threads.